High throughput satellites and methods of operating high throughput satellites for relaying data between low earth orbit satellites to endpoints

ABSTRACT

A high throughput satellite (HTS) and a method of operating the HTS for relaying data between a low earth orbit (LEO) satellite and a target ground station, where the HTS provides spot beams for a spot beam coverage area. The method of operating the HTS includes: determining an estimated trajectory of an orbiting LEO satellite; assigning a plurality of assigned spot beams having a matching color re-use polarization; and transmitting assignments of the plurality of assigned spot beams to the high throughput satellite to cause the high throughput satellite to maintain the inter-satellite link via a first spot beam and one or more assigned subsequent spot beams having the matching color re-use polarization.

RELATED APPLICATION(S)

This patent arises from a continuation of U.S. patent application Ser.No. 16/026,816, (Now U.S. Pat. No. 10,523,312) which was filed on Jul.3, 2018. U.S. patent application Ser. No. 16/026,816 is herebyincorporated herein by reference in its entirety. Priority to U.S.patent application Ser. No. 16/026,816 is hereby claimed.

TECHNICAL FIELD

The present application relates to satellite communications, and moreparticularly to high throughput satellites and methods of operating highthroughput satellites for relaying data from low earth orbit satellitesto endpoints.

BACKGROUND

Earth or space observation satellites collect data including Earthimages, land exploration data, weather observation data, maritimesurveillance data, or forest monitoring data. Earth or space observationsatellites are commonly low Earth orbit (LEO) satellites and orbit theEarth at an altitude in the range of 300 to 1,000 km above the Earth'ssurface. In 2017, approximately 1071 LEO satellites are in orbit and thenumber of LEO satellites to be launched is expected to increase.

LEO satellites require a communication link with a ground station fortelemetry, tracking, and command (TT&C) and for transmitting Earth orspace observation data to one or more ground stations. When used forEarth or space observation, LEO satellites can (1) capture and storeEarth Observation (EO) data in on-board memory as the LEO satelliteorbits the Earth; and (2) transmit the stored EO data when the LEOsatellite has line-of-sight visibility with a ground station during aprocess known as “store and forward”. The duration of time that the LEOsatellite has line-of-sight visibility with the target ground stationdepends on the orbiting altitude and inclination of the LEO satelliteand the latitude of the target ground station. As LEO satellites orbitat relatively low altitudes from the Earth's surface, the duration oftime when the LEO satellite has line-of-sight visibility with a targetground station is typically in the range of 5 to 15 minutes per orbit ofthe Earth. When the LEO satellite has line-of-sight visibility with thetarget ground station, the LEO satellite can transmit data and telemetryto the target ground station and receive commands from the target groundstation. In some scenarios, because the amount of EO data or TT&C datacan be large, the duration of time required to transmit EO data to thetarget ground station can exceed the duration of time that the LEOsatellite may have line-of-sight visibility with the target groundstation. Any EO data or TT&C data not transmitted by the LEO satelliteto the target ground station may continue to be stored in on-boardmemory and transmitted to the target ground station when the LEOsatellite re-establishes line-of-sight visibility on a subsequent orbitof the Earth, thus delaying EO data transmission to the target groundstation. When the EO data has a defined shelf life (e.g., weatherobservation data), delaying transmission of the EO data from the LEOsatellite to the target ground station may render the weatherobservation data to become stale or out-of-date. Further, if TT&C datatransmission and reception at the LEO satellite is delayed, a networkoperations center at the target ground station may be unable to resolveissues or otherwise control the LEO satellite in near real-time or in atimely way.

In some scenarios, to facilitate large amounts of EO and TT&C datatransfer to network operations centers or target ground stations,several successively spaced ground terminals along the Earth's surfacethat corresponds to the trajectory of a given LEO satellite may beprovided. However, building and operating a large number of groundterminals can be costly.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made, by way of example, to the accompanyingdrawings which show example embodiments of the present disclosure, andin which:

FIG. 1 illustrates an example European Data Relay Satellite (EDRS) in ageostationary orbit;

FIG. 2 illustrates an example Tracking and Data Relay Satellite (TDRS)for data relay operations;

FIG. 3 illustrates components of an example Heinrich-Hertz Satellite(H2Sat);

FIG. 4 illustrates a satellite system for relaying data, in accordancewith an example of the present application;

FIG. 5 illustrates spot beam coverage areas provided by respective highthroughput satellites, in accordance with an example of the presentapplication;

FIG. 6 illustrates a spot beam coverage area including single-band spotbeams and multi-band spot beams provided by a high throughput satellite,in accordance with another example of the present application;

FIG. 7 illustrates, in flowchart form, a method of operating a highthroughput satellite for relaying data between one or more low earthsatellites and a target ground station, in accordance with an example ofthe present application;

FIG. 8 illustrates a high throughput satellite system for relaying data,in accordance with an example of the present application;

FIG. 9 illustrates a simplified block diagram of a radio-frequencypayload for a LEO satellite, in accordance with an example of thepresent application; and

FIG. 10 illustrates, in block diagram form, an example high throughputsatellite payload, in accordance with an example of the presentapplication.

Like reference numerals are used in the drawings to denote like elementsand features.

DETAILED DESCRIPTION

In one aspect, the present application describes a method of operating ahigh throughput satellite for relaying data between one or more lowearth orbit (LEO) satellites and a target ground station. The highthroughput satellite provides a plurality of spot beams for a spot beamcoverage area. The method includes: determining an estimated trajectoryof an orbiting LEO satellite travelling through the spot beam coveragearea; assigning, based on the estimated trajectory, a plurality ofassigned spot beams having a matching color re-use polarization formaintaining an inter-satellite link between the orbiting LEO satelliteand the high throughput satellite as the orbiting LEO satellite travelsthrough the spot beam coverage area; and transmitting assignments of theplurality of assigned spot beams to the high throughput satellite tocause the high throughput satellite to maintain the inter-satellite linkvia a first spot beam and one or more assigned subsequent spot beamshaving the matching color re-use polarization.

In another aspect, the present application describes a networkoperations center for controlling operation of a high throughputsatellite relaying data between one or more low earth orbit (LEO)satellites and a target ground station. The high throughput satelliteprovides a plurality of spot beams for a spot beam coverage area. Thenetwork operations center includes: a high speed telemetry and commandlink to the high throughput satellite; a processor; and memory storingprocessor-executable instructions that, when executed by the processor,cause the processor to: determine an estimated trajectory of an orbitingLEO satellite travelling through the spot beam coverage area; assign,based on the estimated trajectory, a plurality of assigned spot beamshaving a matching color re-use polarization for maintaining theinter-satellite link between the orbiting LEO satellite and the highthroughput satellite as the orbiting LEO satellite travels through thespot beam coverage area; and transmit assignments of the plurality ofassigned spot beams to the high throughput satellite to cause the highthroughput satellite to maintain the inter-satellite link via a firstspot beam and one or more subsequent assigned spot beams having thematching color re-use polarization.

In another aspect, the present application provides a high throughputsatellite comprising: a plurality of feeds providing a plurality of spotbeams for a spot beam coverage area; and a digital processor to: receiveassignments of a plurality of assigned spot beams for maintaining aninter-satellite link between an orbiting LEO satellite and the highthroughput satellite as the orbiting LEO satellite travels through thespot beam coverage area; configure, based on an estimated trajectory ofthe orbiting LEO satellite, the plurality of assigned spot beams havinga matching color re-use polarization for maintaining the inter-satellitelink as the orbiting LEO satellite travels through the spot beamcoverage area; establish the inter-satellite link with the orbiting LEOsatellite via a first spot beam of the plurality of assigned spot beams;and transition the inter-satellite link from the first spot beam tosubsequent assigned spot beams having the matching color re-usepolarization as the LEO satellite travels through the spot beam coveragearea.

Other example embodiments of the present disclosure will be apparent tothose of ordinary skill in the art from a review of the followingdetailed description in conjunction with the drawings.

Any feature described in relation to one aspect or embodiment of theinvention may also be used in respect of one or more otheraspects/embodiments. These and other aspects of the present inventionwill be apparent from, and elucidated with reference to, the embodimentsdescribed herein.

In the present application, the term “and/or” is intended to cover allpossible combinations and sub-combinations of the listed elements,including any one of the listed elements alone, any sub-combination, orall of the elements, and without necessarily excluding additionalelements.

In the present application, the phrase “at least one of . . . or . . . ”is intended to cover any one or more of the listed elements, includingany one of the listed elements alone, any sub-combination, or all of theelements, without necessarily excluding any additional elements, andwithout necessarily requiring all of the elements.

Satellites are devices positioned in orbital space and are used forvarious purposes. In one example, satellites are communicationsatellites. That is, they are positioned in orbital space for thepurpose of providing communications. For example, communicationsatellites are designed to relay communication signals between twoend-points (which may be stationary or mobile) to provide communicationservices such as telephone, television, radio and/or internet services.

The satellites may employ a variety of orbital paths around the Earth.For example, satellites may have geostationary orbits, molniya orbits,elliptical orbits, polar and non-polar Earth orbits, etc. Communicationsatellites typically have geostationary orbits. That is, thecommunication satellites have a circular orbit above the Earth's equatorand follow the direction of the Earth's rotation. A satellite in such anorbit has an orbital period equal to the Earth's rotational period, andaccordingly may appear at a fixed position in the sky for groundstations.

Communication satellites are typically spaced apart along thegeostationary orbit. That is, the satellites are positioned in orbitalslots. The satellite operators coordinate use of orbital slots with eachother under international treaty by the International TelecommunicationUnion (ITU), and the separation between slots depends on the coverageand frequency of operation of the satellites. In some examples, theseparation between satellites may be between 2 to 3 degrees of orbitallongitude. In some examples, the separation between satellites may beless than 2 degrees of separation. The separation of satellites in sucha manner allows for frequency reuse for both uplink and downlinktransmission. For example, by separating adjacent satellites by adistance greater than the transmitting beamwidth (i.e., the angle,measured in a horizontal plane, between the directions at which thepower of the beam is at least one-half its maximum value) of an antennaassociated with the ground station for uplink transmission, the samefrequency for the communication signals may be employed to uplink toadjacent satellites with interference at or below the coordinated level.Similarly, if the separated distance between the adjacent satellites isgreater than the receiving beamwidth of the antenna associated with theground station for downlink transmission, the same frequency for thecommunication signals may be employed to downlink from adjacentsatellites with interference at or below the coordinated level.

To perform communication functions, the satellite is equipped withvarious components. For example, the satellite may include acommunication payload (which may further include transponders, one ormore antennas, and switching systems), engines (to bring the satelliteto the desired orbit), tracking and stabilization systems (used toorient the satellite and to keep the satellite in the correct orbit),power subsystems (to power the satellite) and command and controlsubsystems (to maintain communication with ground control stations).

The transponder of the satellite forms a communication channel betweentwo end-points to allow for communications between the two end-points.The transponder also defines the capacity of the satellite forcommunications.

The antenna of the satellite transmits and receives communicationsignals. More specifically, the antenna is an electronic component thatconverts electric currents (which may be generated by a transmitter) forpropagating radio frequency (RF) signal during transmission, andconverts induced RF signals to electric currents during reception. Insome examples, the antenna may be associated with an amplifier which mayamplify the power of the transmitted or received RF signals.

The communication signals may be microwave signals. Microwave signalsare RF signals that have wavelengths ranging from as long as one meterto as short as one millimeter. Equivalently, the frequency of the RFsignals may range from 300 MHz to 300 GHz. More particularly, thecommunication signals are within certain frequency bands of microwavesignals as they are more suited for satellite communications. In someexamples, a satellite may operate within the frequency of the C-banddefined by the ITU. The C-band is a portion of the electromagneticspectrum that ranges from approximately 4 GHz to 8 GHz. That is, thecommunication signals are transmitted by and received at the satellitewithin such a frequency range. In some examples, the satellite mayoperate within frequencies higher than 8 GHz. For example, the satellitemay operate within the frequency of the Ku-band. The Ku-band is theportion of the electromagnetic spectrum that ranges from approximately10 GHz to 18 GHz. In some examples, the satellite may operate withinother high frequencies above the Ku-band. For instance, the satellitemay operate within the Ka-band frequency. The Ka-band is the portion ofthe electromagnetic spectrum that ranges from approximately 26.5 GHz to40 GHz (at present, the assigned slots for fixed satellite service (FSS)are 27-31 GHz for uplink and 17.7-21.2 GHz for downlink). In someexamples, the satellite may be configured to operate in more than oneband. In one example, the satellite may be equipped to receive andtransmit signals within the C-band, Ku-band, and Ka-band. It will beappreciated that the satellites may operate within other microwavefrequency bands. For example, the satellites may operate in any one ofthe defined microwave frequency bands ranging in frequencies fromapproximately 1 GHz to 170 GHz. Examples of other microwave frequencybands include the X-band, Q-band, V-band, etc.

Earth or space observation satellites are commonly deployed fordetecting and capturing data, such as Earth images, land explorationdata, weather observation data, maritime surveillance data, or forestmonitoring data. Earth or space observation satellites are commonly lowEarth orbit (LEO) satellites and orbit the Earth at an altitude in therange of 300 to 1,000 km above the Earth's surface. LEO satellitesrequire a communication link with a target ground station for telemetry,tracking, and command (TT&C) and for transmitting Earth or spaceobservation data to one or more ground stations. When used for Earth orspace observation, LEO satellites can (1) capture and store EarthObservation (EO) data in on-board memory as the LEO satellite orbits theEarth; and (2) transmit the stored EO data when the LEO satellite hasline-of-sight visibility with a ground station during a process known as“store and forward”. The duration of time when the LEO satellite mayhave line-of-sight visibility with a target ground station is typicallyin the range of 5 to 15 minutes per orbit of the Earth, and during thisduration of time the LEO satellite can transmit data and telemetry tothe target ground station and receive commands from the target groundstation. When the amount of EO data or TT&C data is large, the durationof time required to transmit EO data to the target ground station canexceed the duration of time that the LEO satellite has line-of-sightvisibility with the target ground station. Any EO data or TT&C data notyet transmitted to the target ground station may remain stored inon-board memory and transmitted at a later time to the target groundstation when the LEO satellite re-establishes line-of-sight visibilityon a subsequent orbit of the earth or another ground terminal. When EOdata has a defined shelf life (e.g., weather observation data), delayingtransmission of EO data can lead to the data becoming stale orout-of-date. In some configurations, several successively spaced groundterminals may be provided along the Earth's surface that corresponds tothe trajectory of a given LEO satellite such that data can becontinuously transmitted to a subsequent ground station if atransmission of a data set has not completed. However, building,operating, and managing a large number of ground terminals can becostly.

Accordingly, in some scenarios, geostationary (GEO) satellites may beprovided for relaying data between a given LEO satellite (e.g., Earth orspace observation satellite) and a target ground station for providing agreater duration of time which the given LEO satellite may transmit datato the target ground station.

Reference is now made to FIG. 1, which illustrates an example EuropeanData Relay Satellite (EDRS) 100 in a geostationary orbit relative to theEarth 150. The EDRS provides global data relay services to usercommunities associated with the European Space Agency (ESA) and iscurrently a commercially operated data relay satellite. For example, theEDRS 100 is configured to relay data between an example LEO satellite110 and a target ground station 120. The example EDRS 100 utilizes anoptical inter-satellite link (OISL) providing return service (e.g., LEOsatellite→GEO satellite→ground terminal) data rate of up to 1.8 Gbps andforward service (e.g., ground terminal→GEO satellite→LEO satellite) datarate of up to 500 bps for telemetry, tracking, and command (TT&C). Theexample EDRS 100 may also include a Ka-band radio transmitter totransmit data to a ground station. A Ka-band radio transmitter may beimplemented with a steerable reflector antenna providing return servicedata rate of approximately 300 Mbps and forward service data rate of upto 1 Mbps.

Although the EDRS 100 utilizes an optical inter-satellite link thatprovides greater bandwidth, faster data transfer speeds, and lessinterference than radio frequency signalling technologies, the cost ofinstalling optical transceivers on each of the LEO satellite, GEOsatellite, and target ground station is high. Because opticalinter-satellite links are point-to-point communication systems, thenumber data relay paths for LEO satellites to ground terminals islimited by cost. The number of optical laser communication terminalsthat can be installed on-board the respective satellites (e.g., earthdeck of satellites with required field of view) can also be limited. Insome examples, the EDRS 100 may only support data relay for a single LEOsatellite. Further, the optical laser positioning accuracy requirementis higher than the radio frequency signal positioning accuracyrequirements. For example, the radio frequency signal positioningaccuracy is measured in the unit mRad, while the optical laser signalpositioning accuracy is measured in the unit μRad or nRad (e.g., μRad ornRad is 10³ or 10⁶ times higher, respectively, than mRad). Further, theoptical inter-satellite links may be susceptible to interference byclouds or other weather factors.

Reference is now made to FIG. 2, which illustrates an example Trackingand Data Relay Satellite (TDRS) 200 for data relay operations. The TDRS200 utilizes radio frequency signalling technology and includes twosingle access antennas 210, each having a diameter of approximately15-feet for tracking LEO satellites. The single access antennas 210provide data relay communication to a single LEO satellite at a time perantenna. The single access antennas 210 can operate using differentbands including the S-band (2.0 to 3.0 GHz), the Ku-band (13.7 to 15GHz), or the Ka-band (22.5 to 27.5 GHz). For the TDRS 200 to groundcommunication link, a dedicated 2.0 m/2.4 m Ku-band antenna 220 is usedfor providing the communication link between the TDRS 200 and a groundstation at the White Sands Complex in New Mexico.

In addition, the TDRS 200 can include an Omni antenna 230 fortransmission and reception of telemetry, tracking and command (TT&C).The TDRS 200 also includes multiple access antennas 232 implementedusing the S-band frequencies and may use phased-array antennas tocommunicate with multiple satellites simultaneously (e.g., for lowdata-rate communications that generate time-sensitive data). The forwardantenna used for uplink commands may include 15 elements, and the returnantenna used for downlink telemetry may include 32 elements. The TDRS200 may also include solar panels 240.

While the example TDRS 200 can provide high volume data delivery, thedata relay operations are limited to single access. While phased-arrayantennas can support operations for multiple access, examplephased-array antennas can only support transmission and reception of lowdata-rate command and telemetry data. Further, the TDRS 200 communicateswith the specific ground terminal at White Sands Complex in New Mexico,thereby limiting options for transmitting and receiving to and fromseveral other target ground stations. That is, the TDRS 200 maycommunicate with the specific ground terminal at White Sands Complex,limiting any flexibility in transmitting or receiving data to any otherground terminal at the surface of the Earth.

Reference is now made to FIG. 3, which illustrates components of anexample Heinrich-Hertz Satellite (H2Sat) 300. The H2Sat 300 is ageostationary satellite that can provide both high data-rate and lowdata-rate data relay communication links. High data-rate communicationlinks are unidirectional communication links via a multi-beam receivingantenna 310. For example, the multi-beam receiving antenna 310 canprovide a unidirectional link from a LEO satellite to the H2Sat 300using Ka-band frequencies. The multi-beam receiving antenna 310 mayinclude several electronically controlled beams and can serve up to 15communication links simultaneously. The multi-beam receiving antenna 310can include electronically controlled beams for tracking movement of LEOsatellites 350 in orbit. When a tracked LEO satellite moves away fromthe coverage area of a given beam, another beam is switched on oractivated, via a switch matrix for beam switching, to track the orbitingLEO satellite. Thus, while the H2Sat 300 can track LEO satellites movingalong a trajectory path, precisely timed tracking and beam-switchingoperations are needed to track orbiting LEO satellites.

The multi-beam receiving antenna 310 may operate to relay data from LEOsatellites to a gateway station 320, and the gateway station 320 may bein communication with a network control center 322.

The example H2Sat 300 also includes a conical horn antenna 330 forproviding low data-rate communication links for relaying telemetry,tracking, and command data. The conical horn antenna 330 provides a lowdata-rate communication link for up to 10 to 15 LEO satellites within agiven coverage area using time-division multiplexing (TDM).

While the example H2Sat 300 can support data relay for multiple LEOsatellites, the multi-beam receiving antenna 310 has low antennagain-to-noise temperature (G/T) as compared to the TDRS systemillustrated in FIG. 2. Because LEO satellite uplink capabilities may belimited, the antenna gain-to-noise-temperature (G/T) for the LEOsatellite to H2Sat 300 return link can impact the overall available datarate of data relay from the LEO satellite to the gateway station 320.

Further, because the example H2Sat 300 establishes a communication linkwith a single gateway station 320, the H2Sat 300 is unable to supporttransmission of confidential data directly to any other desired groundterminal. Data transmission needs to first be routed through the gatewaystation 320. Further, if the gateway station 320 is subject to naturaldisasters, is unavailable, or cannot support data communication at ratedcommunication speeds due to temporary technical difficulties, the H2Sat300 may be unable to provide data relay services from LEO satellites toground terminals.

As numerous LEO satellites are currently in orbit around the Earth, itis desirable to provide data relay satellites that may respectivelysupport multiple LEO satellites simultaneously. As described above, theexample EDRS 100 of FIG. 1 and the example TDRS 200 of FIG. 2 may beunable to support high volume data relay operations for multiple LEOsatellites. The example H2Sat 300 of FIG. 3 can support data relay forup to 15 LEO satellites via the multi-beam receiving antenna 310.However, the multi-beam receiving antenna 310 (e.g., array-fedreflector) has relatively low G/T attributed to high scan loss andaccordingly impacts the maximum achievable data-rate for respectivecommunication links. Further, with the example H2Sat 300, the returninter-satellite links via the multi-beam receiving antenna 310 isunidirectional and the feeder link (e.g., H2Sat 300 to gateway station320) consists of a single beam supporting only a single gateway station320. Further drawbacks of the H2Sat 300 include susceptibility to rainattenuation on the feeder link and an inability for the H2Sat 300 todirectly relay data to desired target ground terminals in the absence ofthe gateway station 320.

It is desirable to provide a geostationary high throughput satellite forrelaying data between several orbiting LEO satellites and one or moreground terminals for increasing the duration of time that eachrespective LEO satellite can transmit data to one or more groundstations. Such high throughput satellites and methods of operating highthroughput satellites are now provided.

In a conventional fixed-satellite service (FSS) system, one or severallarge spot beams (e.g., a semi-global beam for C-band and a selectednumber of regional beams for Ku-band) are typically used to coverdesired spot beam coverage area.

With a high throughput satellite (HTS) system, a satellite utilizesmultiple narrow spot beams (e.g., 0.6 deg Ka-band or Ku-band beams). Thespot beams are arranged in a pattern to cover a desired area. ExampleHTS systems rely on “color re-use”. Different portions of frequencyspectrum used by different spot beams, or the same portion but using adifferent polarization, are referred to as different “colors”. That is,each color represents a segment of spectrum with a bandwidth andpolarization that can be utilized by a satellite or end user within thecoverage area of the respective spot beam. When using spatialseparation, each color can be re-used by multiple spot beams to increasethe HTS system capacity. In some examples, the HTS system may beconfigured to minimize interference in both downlink and uplink signalsby configuring use of adjacent beams having different colors.

In some scenarios, while utilizing fewer colors can lead to higherinter-beam interference, especially at regions near the edge of coverage(EOC), the overall system throughput may be higher as more bandwidth isallocated to each coverage area. An example HTS system design may use a4-color reuse scheme; but some other systems may have 2-colors,6-colors, 8-colors, or more. In some examples, a 2-color reuse patterncan result in some adjacent beams using the same color.

Reference is now made to FIG. 4, which illustrates a satellite system400 for relaying data, in accordance with an example of the presentapplication. FIG. 4 illustrates the Earth 410 and a LEO satellite 420,such as an Earth observation satellite, and a corresponding orbit path422 around the Earth 410. The LEO satellite 420 may orbit the Earth atan altitude in the range of 300 to 1,000 km above the Earth's surface.The LEO satellite 420 is configured to establish a communication linkwith one or more identified ground stations for TT&C and fortransmitting Earth or space observation data to the identified groundstations. As described, the LEO satellite 420 may be configured tocapture and store observation data and, when the LEO satellite 420establishes line-of-sight visibility with a target ground station (notillustrated in FIG. 4), the LEO satellite 420 may transmit the storedobservation data to the ground station. As the duration of time that theLEO satellite 420 will have line-of-sight visibility with the identifiedground stations for data transmission and reception is in the range of 5to 15 minutes per orbit of the Earth and as the amount of EO data can belarge, the duration of time required to transmit observation data to thetarget ground station can exceed the duration of time that the LEOsatellite has line-of-sight visibility with the target ground station.

To supplement the communication link between the LEO satellite 420 andthe identified ground station for data transmission, the satellitesystem 400 includes a high throughput satellite 430 for relaying databetween the LEO satellite 420 and the target ground station. In FIG. 4,the high throughput satellite 430 has a geostationary orbit 432 aboutthe Earth. The example high throughput satellite 430 is equipped with aplurality of spot beams for transmitting and receiving data. Theplurality of spot beams provides a spot beam coverage area 438. Eachspot beam has a beamwidth that results in a coverage area of eachrespective spot beam at the surface of the Earth. In FIG. 4, thecollection of the plurality of spot beams results is illustrated as aspot beam collective 436 and maps to a spot beam coverage area 438 atthe surface of the Earth 410.

Reference is now made to FIG. 5, which illustrates several spot beamcoverage areas provided respectively by several example high throughputsatellites, in accordance with an example of the present application.FIG. 5 illustrates an example first spot beam coverage area 510 providedby a first high throughput satellite, an example second spot beamcoverage area 520 provided by a second high throughput satellite, and anexample third spot beam coverage area 530 provided by a third highthroughput satellite. The first spot beam coverage area 510 cancorrespond to the spot beam coverage area 438 illustrated in FIG. 4 thatis provided by the high throughput satellite 430. Each of the respectivehigh throughput satellites may be geostationary satellites orbiting theEarth and are positioned at individual orbital slots. Collectively, thehigh throughput satellites can provide spot beams that provide datacommunication links with other endpoint devices that may be locatedthroughout the Earth's surface. In FIG. 5, the spot beam coverage areascan include single-band spot beams such as Ka-band spot beams, Q-bandspot beams, or V-band spot beams.

In FIG. 5, each spot beam has a beamwidth that results in a coveragearea at the surface of the Earth, as indicated by the individualcircles. The spot beams provide circular coverage areas; however, it canbe appreciated that the spot beams may provide a spot beam coverage areaat the surface of the Earth that may appear elliptical in shape at the

Earth's surface. Although the coverage areas are indicated as isolatedcircles, each respective beam gain pattern extends beyond the indicatedcircle. The illustrated circle may indicate a −3dB boundary, forexample.

In the example coverage areas illustrated in FIG. 5, color re-use may beemployed to minimize interference. If enough colors are used, adjacentbeams (i.e., adjacent coverage areas for spot beams) do not use the samecolor, which assists in reducing inter-beam interference. In someexamples, the high throughput satellites may feature hundreds of spotbeams. Spot beams are provided to support both forward (ground terminalto high throughput satellite to LEO satellite) and return (LEO satelliteto high throughput satellite to ground terminal) communication links.Through color re-use, many beams can use the same frequency andpolarization and inter-beam interference is managed through spatialseparation of the coverage areas for respective spot beams. It can beappreciated that use of a large number of colors may result in limitedbandwidth being allocated to each spot beam, negatively impactingthroughput. Color re-use patterns with fewer colors can improve thebandwidth available to each spot beam, but at a cost of higherinter-beam interference. Higher inter-beam interference can adverselyimpact the achievable throughput of the system and can lower spectrumefficiency. Accordingly, high throughput satellite systems areimplemented with fixed color re-use patterns that attempt to balance theabove described factors.

FIG. 5 also illustrates example orbit trajectories 540 of one or moreLEO satellites. The orbit trajectories 540 are illustrated as an overlayon the spot beam coverage areas provided by respective high throughputsatellites (described above).

Reference is made to FIG. 6, which illustrates a spot beam coverage area600 provided by a high throughput satellite, in accordance with anexample of the present application. The example multi-spot beam coveragearea 600 can include a collection of single-band spot beams andmulti-band spot beams. For example, the spot beam coverage area 600 canbe provided using Ka-band spot beams which are illustrated as smallercircles. Further, the spot beam coverage area 600 can also be providedusing Q-band spot beams that are concentric with Ka-band spot beams orprovided using V-band spot beams that are concentric with Ka-band spotbeams. In some examples, the beamwidth of the Q-band spot beams or theV-band spot beams may be larger than the beamwidth of the Ka-band spotbeams.

The collection of single-band spot beams and multi-band spot beams canprovide the spot beam coverage area 600 and the high throughputsatellite may support communication links with LEO satellites (e.g.,inter-satellite links) using Ka-band, Q-band, V-band, or other frequencybands as desired.

As described, a respective high throughput satellite can be configuredto provide a plurality of single-band spot beams (see e.g., FIG. 5) or acollection of both single-band spot beams and multi-band spot beams (seee.g., FIG. 6) for a spot beam coverage area. As will be described whenthe high throughput satellite provides multiple spot beams for the spotbeam coverage area 600, the high throughput satellite may simultaneouslyrelay data between multiple LEO satellites and multiple target groundterminals. Further, because the high throughput satellite relays datafrom the respective LEO satellites to one or more target groundterminals, the duration of time that respective LEO satellites maycommunicate with one or more target ground terminals may be greater thanwhen the respective LEO satellites transmit data directly to the one ormore target ground terminals.

In FIG. 6, example single-band spot beams are identified with referencenumbers ranging from S1 to S14. In some examples, the single-band spotbeams may be Ka-band spot beams. In FIG. 6, some of the spot beamsintersect with the orbiting trajectory of a LEO satellite. When the LEOsatellite orbits the Earth, the LEO satellite can include a trackingantenna for tracking the high throughput satellite (e.g.,geostationary). As the LEO satellite orbits the Earth, the LEO satellitemay enter and, subsequently, exit successive coverage areas ofindividual spot beams along the path of LEO satellite orbit.

When the LEO satellite orbits the Earth, the high throughput satellitemay establish an inter-satellite communication link with the first spotbeam identified with reference numeral S1 (FIG. 6). As the LEO satellitecontinues along the orbiting trajectory path, the high throughputsatellite may handover or transition the inter-satellite communicationlink to a subsequent spot beam, such as the spot beam identified withreference numeral S2, and subsequently to spot beams identified withreference numerals S3 to S14.

A high throughput satellite may be configured to provide a single-band(e.g., Ka-band) spot beam having a beamwidth in the range of 0.6 to 1.2degrees and having a spot beam diameter in the range of 400 to 900kilometers. A given LEO satellite may be orbiting the Earth at a highrate of speed that causes the LEO satellite to enter and, subsequently,exit respective coverage areas of spot beams within a short duration oftime. Because a given LEO satellite may be orbiting the Earth at arelatively high rate of speed, to maintain the inter-satellite linkbetween the high throughput satellite and the given LEO satellite fordata communication, frequent spot-beam handover within the spot beamcoverage area (e.g., spot beam coverage area 600 of FIG. 6) may berequired. To minimize the number of occurrences of spot-beam handoveroperations, the high throughput satellite could be configured to providesingle-band (e.g., Ka-band) spot beams having a larger beamwidth.However, spot-beams with larger beamwidths may have poorer antennagain-to-noise-temperature (G/T) ratios as compared to spot-beams withsmaller beamwidths.

The poorer antenna G/T ratios can result in degraded communication linkperformance. Thus, it may be desirable to provide high throughputsatellites and methods for operating the high throughput satellites forefficiently handling spot-beam handover when a given LEO satelliteorbits the Earth and travels through the spot beam coverage area (e.g.,spot beam coverage area 600 of FIG. 6).

Reference is now made to FIG. 7, which illustrates, in flowchart form, amethod 700 of operating a high throughput satellite for relaying databetween one or more LEO satellites and a target ground station, inaccordance with an example of the present application. An example highthroughput satellite can include the high throughput satellite 430illustrated in FIG. 4 in a geostationary orbit relative to the Earth 410(FIG. 4). The example high throughput satellite provides a plurality ofspot beams for a spot beam coverage area. The spot beam coverage areacan include a collection of single-band coverage areas for respectivespot beams as illustrated in FIG. 5 (e.g., respective spot beam coverageareas identified with reference numeral 510, 520, or 530) or acollection of single-band coverage areas and multi-band coverage areasfor respective spot beams as illustrated in FIG. 6. The method 700 ofFIG. 7 includes operations that are carried out by one or moreprocessors at a ground network operations center (NOC) or a groundstation.

At operation 710, the processor determines an estimated trajectory of anorbiting LEO satellite travelling through the spot beam coverage area.For example, in FIG. 6, the estimated trajectory of the orbiting LEOsatellite may be the trajectory visually depicted and identified withreference numeral 650. The trajectory of the orbiting LEO satellite mayinclude a set of latitude/longitude information associated with arunning list of time information. In some examples, the networkoperations center or ground station may estimate the trajectory of theorbiting LEO satellite based on the orbital path of the

LEO satellite at prior points in time.

As described, the high throughput satellite may utilize color re-useschemes for reducing inter-beam interference. That is, color-reuseschemes can utilize different portions of frequency spectrum and/ordifferent polarizations for reducing inter-beam interference. Becausethe duration of time required for the high throughput satelliteutilizing frequency transition to handover communication links from agiven spot beam in the spot beam coverage area to a subsequent spot beammay be less than when the high throughput satellite utilizespolarization transition, it is desirable for the high throughputsatellite to utilize frequency transition when handing overcommunication links from a given spot beam to a subsequent spot beam.

At operation 720, the processor may assign, based on the estimatedtrajectory of the orbiting LEO satellite, a plurality of assigned spotbeams having a matching color re-use polarization for maintaining aninter-satellite link between the orbiting LEO satellite and the highthroughput satellite as the orbiting LEO satellite travels through thespot beam coverage area. As described, because a given LEO satellite maybe orbiting the Earth at a high rate of speed, the LEO satellite mayenter and, subsequently, exit a respective coverage area of a spot beamin a short duration of time. As the orbiting LEO satellite may be withinthe respective coverage area of a particular spot beam for a specificduration of time, the specific duration of time may be less than theduration of time needed if communication link handover usingpolarization transition was used. If the high throughput satelliteutilizes polarization transition, once communication link handover iscompleted from a given spot beam to a subsequent spot beam, the LEOsatellite may already have travelled to further subsequent spot beams inthe LEO satellite trajectory. To ameliorate the challenges associatedwith using polarization transition, the processor assigns one or moresubsequent spot beams having the matching color re-use polarization formaintaining the inter-satellite link.

To illustrate, as described with reference to FIG. 6, when the LEOsatellite orbits the Earth, the high throughput satellite may establishan inter-satellite communication link with the first spot beamidentified with reference numeral S1 (FIG. 6). The high throughputsatellite can identify, based on the estimated trajectory of theorbiting LEO satellite, when the orbiting LEO satellite may approach the−3 dB gain boundary or travel outside the −3 dB boundary of the firstspot beam S1. Based on spot beam assignments received from the groundnetwork operations center, the high throughput satellite can identifythat a subsequent spot beam, such as the spot beam identified withreference numeral S2 (FIG. 6), is along the estimated trajectory of theorbiting LEO satellite and enable that subsequent spot beam having acolor re-use polarization that matches the first spot beam S1.

That is, if that subsequent spot beam (S2) has a color re-usepolarization that matches the first spot beam S1, the network operationscenter can assign that subsequent spot beam (S2) to be in the assignedplurality of spot beams for maintaining the inter-satellite link betweenthe orbiting LEO satellite and the high throughput satellite. Theprocessor of the network operations center can iteratively determinewhich spot beams in the plurality of high throughput satellite spotbeams have a matching color re-use polarization that may be assigned formaintaining the inter-satellite link between the particular orbiting LEOsatellite and the high throughput satellite.

In some examples, the processor at the network operations center candetermine and assign an available frequency slot in the respectiveassigned one or more subsequent spot beams (described above) that hasthe same color re-use polarization for the anticipated time that theorbiting LEO satellite will enter the respective assigned subsequentspot beam. That is, the processor may determine, based on a spot beamcoverage area satellite traffic status report, an available frequencyslot and time associated with the available frequency slot, and canassign that available frequency slot to a respective LEO satellite.

In some examples, prior to assigning the plurality of assigned spotbeams for maintaining the inter-satellite link, the processor at thenetwork operations center overlays a spot beam coverage area map for thehigh throughput satellite on the determined estimated trajectory of theorbiting LEO satellite for identifying the one or more subsequent spotbeams available for maintaining the inter-satellite link. For example,referring again to FIG. 6, the processor may overlay the determinedestimated trajectory 650 of the orbiting LEO satellite on the spot beamcoverage area 600 associated with the high throughput satellite. In someexamples, the spot beam coverage area 600 may be associated withinformation regarding frequency spectrum portions and polarization forthe individual spot beams such that the processor may graphicallyidentify the one or more subsequent spot beams having a matching colorre-use polarization for use to maintain the inter-satellite link as theorbiting LEO satellite travels through the spot beam coverage area.

When the number of inter-satellite links between the high throughputsatellite and respective LEO satellites is large, it can be challengingto graphically and/or visually identify the one or more requiredsubsequent spot beams, described above. As an alternative, in someexamples, the processor aggregate or collect trajectory information forthe LEO satellites and information on frequency spectrum portions andpolarization associated with the individual spot beams. The processormay, subsequently, determine based on the collected information the oneor more subsequent spot beams having a matching color re-usepolarization for maintaining the inter-satellite link.

In some scenarios, when numerous trajectories of respective LEOsatellites pass through a portion of the spot beam coverage area that isprovided by the high throughput satellite, that particular portion ofthe spot beam coverage area may include a dense demand for communicationlinks. To ameliorate challenges associated with non-uniform distributionof communication link demand across the spot beam coverage area, in someexamples, the high throughput satellite can support dynamic beamforming.When the high throughput satellite supports beamforming, prior toassigning the plurality of assigned spot beams for maintaining theinter-satellite link (e.g., operation 720), the processor mayre-configure the plurality of assigned spot beams of the spot beamcoverage area in response to determining that a number ofinter-satellite links between the high throughput satellite and aplurality of respective LEO satellites is greater than a thresholdnumber. That is, the processor can utilize beamforming operations forproviding a re-configured spot beam coverage area to alleviatechallenges associated with the existing spot beam coverage areaexperiencing non-uniform distribution of data throughput demand forestablishing or maintaining inter-satellite links.

At operation 730, the processor transmits assignments of the pluralityof assigned spot beams to the high throughput satellite to cause thehigh throughput satellite to maintain the inter-satellite link via afirst spot beam and one or more subsequent assigned spot beams havingthe matching color re-use polarization. Transition of theinter-satellite link from the first spot beam to the one or moreassigned subsequent spot beams utilizes frequency transition. It can beappreciated that when the network operations center transmitsassignments of the plurality of assigned spot beams to the highthroughput satellite, the high throughput satellite can scheduleconfigurations of the respective spot beams (e.g., frequency slot, gainsetting, etc.) for establishing or enabling the inter-satellite link ata time that the LEO satellite is anticipated to be within the boundaryof the respective spot beams.

In some examples, the processor of the ground NOC can amend modulationand coding (MODCOD) operations. The processor may monitor feeder linkperformance and, in response to degrading or fluctuating feeder linkperformance, the processor may alter MODCOD operations for maintainingthe feeder link performance to mitigate rain fade or other weatherconditions by requesting the LEO to change the MODCOD of on-board modemshown in FIG. 9. Altering MODCOD operations is based on adaptive codingand modulation (ACM) functions of DVB-S2 or DVB-S2X standards at theground NOC modem. For example, the ground NOC modem can transmit feederlink performance status information to a LEO satellite modem, and theground NOC modem can transmit commands to the LEO satellite such thatthe LEO satellite may alter MODCOD operations for maintaining the feederlink at a desired performance level.

The high throughput satellite described herein provides spot beams for aspot beam coverage area. The respective spot beams for providing theinter-satellite link can support data communication using at least oneof Ka-band, Q-band, or V-band frequency spot beams. Referring again toFIG. 5, the plurality of spot beams for the first spot beam coveragearea 510, the second spot beam coverage area 520, or the third spot beamcoverage area 530 can be any one of Ka-band, Q-band, or V-band frequencyspot beams.

In another example, the respective spot beams for the spot beam coveragearea can include a combination of single-band spot beams and multi-bandspot beams. For example, referring again to FIG. 6, the plurality ofspot beams for the spot beam coverage area 600 can include a combinationKa-band/Q-band multi-band spot beams or Ka-band /V-band multi-band spotbeams. That is, the high throughput satellite can include a plurality ofspot beam antennas or feeds, where each spot beam antenna can provideone or more coverage areas. In some examples, a spot beam antenna orfeed can provide a multi-band spot beam, where the spot beam antenna cangenerate a first frequency band spot beam and a second frequency bandspot beam concentric with the first frequency band spot beam. In thisexample, the first frequency band spot beam can have a differentbeamwidth than the second frequency band spot beam.

To illustrate, reference is made again to FIG. 6, where the example spotbeam coverage area 600 includes several multi-band spot beams. For easeof exposition, only a single multi-band spot beam is identified in FIG.6. The identified multi-band spot beam can include a Ka-band spot beam682 and a Q-band spot beam 684. Because the Q-band spot beam 684 has alarger beamwidth than the Ka-band spot beam 682, the number of spot beamantennas for providing Q-band spot beams 684 in the spot beam coveragearea 600 may be less than the number of spot beam antennas for providingKa-band spot beams. Although the example multi-band spot beam isdescribed using Ka-band and Q-band, other ITU frequency bands may beimplemented.

Reference is now made to FIG. 8, which illustrates a HTS system 800 forrelaying data between one or more LEO satellites and one or more targetground stations, in accordance with an example of the presentapplication.

The HTS system 800 includes a first high throughput satellite 810. Thefirst high throughput satellite 810 can be a geostationary satellite.The first high throughput satellite 810 can provide a plurality of spotbeams for providing a first spot beam coverage space 812. The first spotbeam coverage space 812 includes a combination of spot beams arranged toprovide a first spot beam coverage area, for example, at the surface ofthe Earth.

As illustrated in FIG. 8, a first LEO satellite 814 is within theboundary of the first spot beam coverage space 812. Thus, the first highthroughput satellite 810 may establish an inter-satellite link 870 withthe first orbiting LEO satellite 814. Further, as illustrated in FIG. 8,a first ground terminal 818 is within the boundary of the first spotbeam coverage space 812. The first high throughput satellite 810 mayestablish a first feeder link 872 with the first ground terminal 818.

As described herein, LEO satellites can capture and store earthobservation data and, subsequently, transmit the stored EO data when theLEO satellite has line-of-sight visibility with a target groundterminal. For example, in FIG. 8, the first LEO satellite 814 provides afirst direct-to-ground terminal space 816, such that when the targetground terminal is within range of the direct-to-ground terminal space816, the LEO satellite 814 may transmit data to the target groundterminal.

When the LEO satellite does not have line-of-sight visibility with thetarget ground terminal, the LEO satellite can continue storing captureddata. As described herein, because the LEO satellite orbits atrelatively low altitudes from the Earth's surface, the duration of timewhen the first ground terminal 818 may be within range of thedirect-to-ground terminal space 816 may be in the range of 5 to 15minutes. To ameliorate the disadvantages of relying solely on datatransmission from the first LEO satellite 814 directly to the firstground terminal 818 in the duration of time when line-of-sightvisibility is available, the first LEO satellite 814 can utilize acombination of: (1) the data transmission from the first LEO satellite814 directly to the first ground terminal 818, when the first LEOsatellite 814 has line-of-sight visibility with the first groundterminal 818; and (2) data relay via the first inter-satellite link 870and the first feeder link 872 for increasing the duration of timeavailable for (a) data transmission from the first LEO satellite 814 tothe first ground terminal 818; and (b) data reception at the first LEOsatellite 814 from the first ground terminal 818.

In FIG. 8, the example first high throughput satellite 810 includes thefirst spot beam coverage space 812 providing a spot beam coverage areaspanning approximately one-third of the Earth's surface. If a secondhigh throughput satellite 820 and a third high throughput satellite 830are spaced in geostationary orbit slots that are substantiallyequidistant from a neighbouring high throughput satellite, thecombination of the first high throughput satellite 810, the second highthroughput satellite 820, and the third high throughput satellite 830can relay data between a respective LEO satellite and a target groundstation to provide a greater duration of time for data transmission thanif the respective LEO satellite relied solely on a communication linkwithin the boundary of the respective direct-to-ground terminal space(see e.g., the first direct-to-ground terminal space 816). Thecombination of the first high throughput satellite 810, the second highthroughput satellite 820, and the third high throughput satellite 830for relaying data can result in providing data communicationtransmission coverage for a substantial portion of the Earth's surface.

In the example HTS system 800 of FIG. 8, respective inter-satellitelinks support data communication using at least one of Ka-band, Q-band,and/or V-band frequency spot beams. Further, the respective feeder linkssupport data communication using Ka-band frequency spot beams. In someexamples, spot beams configured with other ITU frequency band signalscan be implemented.

As an illustrative example, in FIG. 8, when an orbiting LEO satellite,such as the first LEO satellite 814, has line-of-sight visibility withthe first high throughput satellite 810 via a first spot beam, aninter-satellite link is formed between the orbiting LEO satellite andthe first high throughput satellite 810. Referring again to FIG. 6, thefirst spot beam can be the first spot beam identified with referencenumeral S1.

In some examples, subsequent to the first LEO satellite establishing aninter-satellite link between the orbiting LEO satellite and the highthroughput satellite, the processor of the ground NOC can identify atarget ground station from a plurality of ground stations within thespot beam coverage area for supporting feeder link communicationsbetween the high throughput satellite and the target ground station. Theorbiting LEO satellite can transmit information regarding the targetground station to the ground NOC, and the ground NOC can send commandsto the high throughput satellite for instructing that a feeder link beestablished with the identified target ground station.

Because the high throughput satellite provides a plurality of spot beamsfor the spot beam coverage area 600, the ground NOC can instruct thehigh throughput satellite to establish a feeder link to support feederlink communication between the high throughput satellite and any of theground stations that may be within the spot beam coverage area 600. Insome examples, once the inter-satellite link is established, theorbiting LEO satellite may specify the particular ground terminal towhich data is to be transmitted and the high throughput satellite canestablish the feeder link with the target ground terminal. That is, adigital processor or a digital channelizer of the high throughputsatellite can: (1) digitize incoming radio frequency signals receivedfrom a LEO satellite into respective sub-channels; and (2) route theindividual sub-channels to the target ground station at desired gain andfrequency settings.

The high throughput satellite can establish a feeder link using anynumber of frequency band spot beams. For example, to mitigate or reduceweather effects or rain attenuation on the feeder link, the highthroughput satellite may establish the feeder link using Ka-band spotbeams or Ku-band spot beams. Ka-band spot beams or Ku-band spot beamsmay be less susceptible to rain attenuation than Q-band or V-band spotbeams. Spot beams operating in frequency bands having higher frequenciesare more susceptible to link degradation due to rain attenuation.

Further, to mitigate effects of rain attenuation, the high throughputsatellite can be configured to utilize adaptive coding and modulation(ACM) and on-board digital routing. For example, ACM operations canmitigate rain attenuation effects by altering the Forward ErrorCorrection (FEC) code and modulation to compensate for rain fade. Inaddition, the high throughput satellite can configure an on-boarddigital channelizer for routing data transmission to alternate groundterminals where rain attenuation effects may be less prevalent. Thus,the high throughput satellite may route, via an on-board digitalchannelizer, uplink data from an orbiting LEO satellite to (1) anexisting feeder link associated with a target ground terminal of thehigh throughput satellite; or (2) an alternate feeder link with adifferent target ground terminal specified by the orbiting LEOsatellite.

The respective spot beams for providing feeder links between the highthroughput satellite and the ground station may support communicationusing at least one of Ka-band spot beams or Ku-band spot beams. Spotbeams operating in other ITU frequency bands may also be used forproviding the feeder link.

It can be appreciated that when an inter-satellite link is establishedbetween the LEO satellite and the high throughput satellite at the firstspot beam, the LEO satellite may receive, via the high throughputsatellite and from the ground NOC, information relating to assignment ofthe plurality of assigned spot beams having a matching color re-usepolarization. The LEO satellite may also receive information relating tothe spot beam coverage areas of the high throughput satellite. Thus,when the LEO satellite orbits the Earth along the planned LEO satellitetrajectory, the LEO satellite may, based on global positioning systemlocation information, configure the antennas of the LEO satellite toalter its frequency of transmission or reception of data as the LEOsatellite travels into and away from respective spot beams of the spotbeam coverage areas.

Reference is now made to FIG. 9, which illustrates a simplified blockdiagram of an example radio-frequency payload 900 installed on anexample LEO satellite, in accordance with an example of the presentapplication. Example LEO satellites, such as the first LEO satellite 814of FIG. 8, can be equipped with a tracking antenna 902 for tracking ahigh throughput satellite when the first LEO satellite 814 travels alongits orbit path. In some examples, the tracking antenna 902 can includemechanical antenna turning mechanisms, switched beams, reflector arrays,phased arrays, di-electric lensing, or metamaterial arrays. In someexamples, the rotation speed of the tracking antenna can be 10degrees/second or faster.

In FIG. 9, the example tracking antenna 902 is a phased-array trackingantenna. The phased-array tracking antenna can utilize constructiveinterference of an array of antennas of which individual antennas arephase shifted. The example radio-frequency payload 900 can include oneor more filters, such as band pass filters (BPF), and one or moreamplifiers, such as high-power amplifiers (HPA) or low-noise amplifiers(LNA). The example radio-frequency payload 900 may also include an UpConverter (UCo) and a Down Converter (DonCo).

Reference is now made to FIG. 10, which illustrates, in block diagramform, an example high throughput satellite payload 1000. The highthroughput satellite payload 1000 includes N spot beam antennas 1002.The high throughput satellite payload 1000 includes a plurality of feedsproviding a plurality of spot beams for a spot beam coverage area. Theplurality of feeds can transmit or receive radio frequency signals fromorbiting LEO satellites, ground terminals, or other endpoints.

Signals received in one of the spot beam antennas 1002 are amplified bylow noise amplifiers (LNA) 1004, down-converted in mixers 1006, andinput to a digital processor (DP) 1008. The digital processor 1008digitizes the down-converted spectrum to produce digitized spectrum toenable fast analysis and switching operations, including channelswitching or reassignment. Generally, the digital processor 1008 candigitize incoming or detected radio-frequency signals into individualsub-channels and route the individual sub-channels to desired downlinkspots with configured gain settings and in accordance with frequencyslot allocations. The digitized channels are output by the digitalprocessor 1008 for up-conversion, amplification (typically via travelingwave tube 1010), and transmission via the antennas 1002.

The digital processor 1008 may also implement one or more operations forrelaying data between one or more low earth orbit (LEO) satellites and atarget ground station. For example, the digital processor 1008 canreceive, from ground NOC or ground terminals, assignments of a pluralityof assigned spot beams for maintaining an inter-satellite link betweenan orbiting LEO satellite and the high throughput satellite payload 1000as the orbiting LEO satellite travels through a spot beam coverage areaprovided by the high throughput satellite payload 1000. The digitalprocessor 1008 can configure a plurality of assigned spot beams having amatching color re-use polarization for maintaining the inter-satellitelink as the orbiting LEO satellite travels through the spot beamcoverage area. The digital processor 1008 can establish theinter-satellite link with the orbiting LEO satellite via a first spotbeam of the plurality of assign spot beams. Further, the digitalprocessor 1008 can transition the inter-satellite link from the firstspot beam to subsequent assigned spot beams having the matching colorre-use polarization as the LEO satellite travels through the spot beamcoverage area. That is, the digital processor 1008 can configure thefirst spot beam and subsequent assigned spot beams at respective andsuccessive points in time based on assigned frequency slots or gainsettings for enabling and establishing inter-satellite links with theorbiting LEO satellite as it travels through the first spot beam andsubsequent assigned spot beams.

In some examples, the high throughput satellite can be configured toestablish inter-satellite and feeder links according to thespecifications summarized in Table 1.

TABLE 1 ISL/Feeder Link Frequency Access Scheme ISL Ka-band/Ka-band &Q-band Support multiple (LEO-to-GEO HTS) multi-band spot beams; OR usersfor data and Ka-band/Ka-band & V-band telemetry delivery multi-band spotbeams Feeder link Ka-band spot beams (GEO HTS-to-Ground) Feeder linkKa-band spot beams Support multiple (Ground-to-GEO HTS) users forsending ISL Ka-band/Ka-band & Q-band commands (GEO HTS-to-LEO)multi-band spot beams; OR to LEO Ka-band/Ka-band & V-band multi-bandspot beams

The high throughput satellite payload 1000 may communicate with a groundnetwork operations center (NOC) 1020, or sometimes known as a groundterminal, by way of high-speed telemetry and command link forcommunicating metadata and connection parameters to the ground networkoperations center 1020, and for receiving configuration and settingsinstructions from the network operations center 1020. The networkoperations center 1020 may include one or more servers and software forimplementing a network management function to manage the configurationand traffic flow of the high throughput satellite payload 1000.

The network operations center 1020 may implement a portion or all of theoperations of the methods described herein. For example, the networkoperations center 1020 may be implemented for controlling operation of ahigh throughput satellite relaying data between one or more LEOsatellites and a target ground station. The network operations center1020 includes a high speed telemetry and command link to the highthroughput satellite, a processor, and memory storingprocessor-executable instructions that, when executed by the at leastone processor, cause the processor to: determine an estimated trajectoryof an orbiting LEO satellite travelling through the spot beam coveragearea; assign, based on the estimated trajectory, a plurality of assignedspot beams having a matching color re-use polarization for maintainingthe inter-satellite link between the orbiting LEO satellite and the highthroughput satellite as the orbiting LEO satellite travels through thespot beam coverage area; and transmit assignments of the plurality ofassigned spot beams to the high throughput satellite to cause the highthroughput satellite to maintain the inter-satellite link via a firstspot beam and one or more subsequent assigned spot beams having thematching color re-use polarization. Transition of the inter-satellitelink from the first spot beam to the one or more assigned subsequentspot beams utilizes frequency transition.

In some examples, the downloadable data volume when a LEO satellitecompletes one pass or orbit about the Earth can be in the range of 400to 900 gigabits per pass. The downloadable data volume can be dependenton spot beam frequency bands implemented, uplink equivalentisotropically radiated power (EIRP) associated with the LEO satellite,antenna gain-to-noise-temperature (G/T) associated with the LEOsatellite, antenna size at the ground terminal for receiving datacommunications, available bandwidth at the high throughput satellite,and the duration of time available for direct data transmission from theLEO satellite to the target ground terminal.

As described, the network operations center 1020 may be implementedusing one or more processors executing machine-readable instructions forcausing the one or more processors to carry out the describedoperations.

In an illustrative example, a high throughput satellite may beimplemented with the below detailed inter-satellite link and feeder linkbudget at different bandwidths, as summarized in Table 2. Table 2provides example downloadable data volume estimates on each LEOsatellite orbit about the Earth. For example, when Ka-band spot beamsare used with 72 MHz bandwidth for data delivery, the volume ofdownloadable data per LEO satellite orbit about the Earth isapproximately 430 Gbits. When higher bandwidths are used, the volume ofdownloadable data per LEO satellite orbit about the Earth is greater.

TABLE 2 ISL Link (LEO-to-GEO) Carrier Frequency (GHz) 30.0 30.0 30.0Ka-band LEO Tx Ant. Diam. (cm) 40.0 40.0 40.0 LEO Tx pwr (W) 50.0 50.050.0 LEO EIRP (dBW) 55.3 55.3 55.3 Bandwidth (MHz) 72.0 125.0 200.0Occupied BW UL PSD (dBW/40 kHz) 22.7 20.3 18.3 FSPL (dB) 213.0 213.0213.0 LEO-to-GEO GEO G/T (dB/K) 18.0 18.0 18.0 HTS spot G/T C/N (dB)11.3 8.9 6.8 Feeder link (GEO-to-Ground) Carrier frequency (GHz) 20.020.0 20.0 Ka-band GEO EIRP/cxr (dBW) 48.6 51.0 53.0 DL EIRP density−30.0 −30.0 −30.0 (dBW/Hz) FSPL (dB) 209.6 209.6 209.6 GEO-to-GroundRain fade at 99.9% 10.0 10.0 10.0 link avail. (dB) Atmospheric loss (dB)1.5 1.5 1.5 7 m Gateway G/T (dB/K) 34.9 34.9 34.9 C/N (dB) 13.4 13.413.4 Total C/N (dB) 9.2 7.5 6.0 Spectral Efficiency 2.1 1.9 1.6 DVB-S2(bit/sym) EN_30230702v010101a Downloadable Data 430.0 659.9 917.2Transmittable per Pass (Gb) data per pass within available time window

The example high throughput satellites and methods of operating highthroughput satellites described herein can facilitate data relayoperations between multiple LEO satellites and one or more target groundstations at a given time. Further, the method of operating highthroughput satellites described herein can ameliorate inefficiencies ofa LEO satellite transmitting data from the LEO satellite to a targetground terminal only during such time that the LEO satellite hasline-of-sight visibility with the target ground terminal. By utilizing acombination of (1) data transmission from a LEO satellite direction to atarget ground terminal when the LEO satellite has line-of-sightvisibility with the target ground terminal; and (2) data relay via ahigh throughput satellite, the duration of time for transmitting datafrom the LEO satellite to the target ground terminal is increasedcompared to when data transmission occurs solely when the LEO satellitehas line-of-sight visibility with the target ground terminal. As anillustrating example, when the LEO satellite solely relies on datatransmission to a target ground terminal when the LEO satellite hasline-of-sight visibility with the target ground terminal, the durationof time available data transmission is typically in the range of 5 to 15minutes per orbit of the Earth. When the LEO satellite relies on bothdata transmission based on line-of-sight visibility with the targetground terminal and data transmission via data relay by a highthroughput satellite, the duration of time available data transmissioncan be on the order 60 minutes or more per orbit of the Earth.

The various embodiments presented above are merely examples and are inno way meant to limit the scope of this application. Variations of theinnovations described herein will be apparent to persons of ordinaryskill in the art, such variations being within the intended scope of thepresent application. Additionally, the subject matter described hereinand in the recited claims intends to cover and embrace all suitablechanges in technology.

1. A method of operating a high throughput satellite for relaying databetween one or more low earth orbit (LEO) satellites and a target groundstation, the high throughput satellite providing a plurality of spotbeams for a spot beam coverage area, the method comprising: determiningan estimated trajectory of an orbiting LEO satellite travelling throughthe spot beam coverage area; identifying, based on the estimatedtrajectory, a set of spot beams in the plurality of spot beams having amatching color re-use polarization for maintaining an inter-satellitelink between the orbiting LEO satellite and the high throughputsatellite as the orbiting LEO satellite travels through the spot beamcoverage area; and transmitting information identifying the spot beamsin the set of spot beams to the high throughput satellite to cause thehigh throughput satellite to maintain the inter-satellite link via asequence of spot beams in the set having the matching color re-usepolarization.
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 10. (canceled) 11.A network operations center for controlling operation of a highthroughput satellite relaying data between one or more low earth orbit(LEO) satellites and a target ground station, the high throughputsatellite providing a plurality of spot beams for a spot beam coveragearea, the network operations center comprising: a high speed telemetryand command link to the high throughput satellite; a processor; andmemory storing processor-executable instructions that, when executed bythe processor, cause the processor to: determine an estimated trajectoryof an orbiting LEO satellite travelling through the spot beam coveragearea; identify, based on the estimated trajectory, a set of spot beamsin the plurality of spot beams having a matching color re-usepolarization for maintaining the inter-satellite link between theorbiting LEO satellite and the high throughput satellite as the orbitingLEO satellite travels through the spot beam coverage area; and transmitinformation identifying the spot beams in the set of spot beams to thehigh throughput satellite to cause the high throughput satellite tomaintain the inter-satellite link via a sequence of spot beams in theset having the matching color re-use polarization.
 12. (canceled) 13.(canceled)
 14. (canceled)
 15. A high throughput satellite comprising: aplurality of feeds providing a plurality of spot beams for a spot beamcoverage area; and a digital processor to: receive informationidentifying a set of spot beams in the plurality of spot beams formaintaining an inter-satellite link between an orbiting LEO satelliteand the high throughput satellite as the orbiting LEO satellite travelsthrough the spot beam coverage area; configure, based on an estimatedtrajectory of the orbiting LEO satellite, a sequence of the spot beamsin the set having a matching color re-use polarization for maintainingthe inter-satellite link as the orbiting LEO satellite travels throughthe spot beam coverage area; establish the inter-satellite link with theorbiting LEO satellite via a first spot beam of the sequence of spotbeams; and transition the inter-satellite link from the first spot beamto subsequent spot beams in the sequence having the matching colorre-use polarization as the LEO satellite travels through the spot beamcoverage area.
 16. (canceled)
 17. (canceled)
 18. (canceled) 19.(canceled)
 20. (canceled)
 21. The method of claim 1, whereintransmitting includes transmitting a command to the high throughputsatellite to be relayed to LEO satellite to alter modulation and coding(MODCOD) operations at the LEO satellite.
 22. The method of claim 21,further comprising monitoring performance status of a feeder link fromthe high throughput satellite to the target ground station, and whereinthe transmitting a command is performed in response to the performancestatus of the feeder link.
 23. The method of claim 22, whereinmonitoring includes detecting degradation of the performance status andthe command includes alterations to the MODCOD operations to mitigateweather conditions that degrade the feeder link performance.
 24. Themethod of claim 21, further comprising monitoring performance status ofa feeder link from the high throughput satellite to the target groundstation, and wherein transmitting includes transmitting feeder linkperformance status information to the high throughput satellite to berelayed to LEO satellite.
 25. The method of claim 24, further comprisingaltering MODCOD operations at the LEO satellite based on the transmittedfeeder link performance status information.
 26. The method of claim 1,wherein the high throughput satellite includes an on-board digitalprocessor, and wherein transmitting includes transmitting a command tothe high throughput satellite to employ adaptive coding and modulation(ACM) and on-board digital routing using its on-board digital processor.27. The method of claim 26, wherein ACM includes adaptive forward errorcorrection and modulation to compensate for rain fade on a feeder linkfrom the high throughput satellite to the target ground station.
 28. Themethod of claim 1, further comprising, at the high throughput satellite,digitally channelizing uplink data from the LEO satellite received overthe inter-satellite link and routing the digitally channelized uplinkdata to a different ground terminal specified by the LEO satellite. 29.The method of claim 28, wherein the routing is carried out in responseto detection of a degraded feeder link to the target ground station. 30.The network operations center of claim 11, wherein the instructions,when executed by the processor, cause the processor to transmit acommand to the high throughput satellite to be relayed to LEO satelliteto alter modulation and coding (MODCOD) operations at the LEO satellite.31. The network operations center of claim 30, wherein the instructions,when executed by the processor, are to further cause the processor tomonitor performance status of a feeder link from the high throughputsatellite to the target ground station, and wherein the processortransmits the command in response to the performance status of thefeeder link.
 32. The network operations center of claim 31, wherein theprocessor monitors performance status by detecting degradation of theperformance status and the command includes alterations to the MODCODoperations to mitigate weather conditions that degrade the feeder linkperformance.
 33. The network operations center of claim 30, furthercomprising monitoring performance status of a feeder link from the highthroughput satellite to the target ground station, and wherein theprocessor transmits the command by transmitting feeder link performancestatus information to the high throughput satellite to be relayed to LEOsatellite.
 34. The network operations center of claim 33, wherein thecommand is to cause altered MODCOD operations at the LEO satellite basedon the transmitted feeder link performance status information.
 35. Thenetwork operations center of claim 11, wherein the high throughputsatellite includes an on-board digital processor, and wherein theinstructions, when executed by the processor, cause the processor totransmit a command to the high throughput satellite to employ adaptivecoding and modulation (ACM) and on-board digital routing using itson-board digital processor.
 36. The network operations center of claim35, wherein ACM includes adaptive forward error correction andmodulation to compensate for rain fade on a feeder link from the highthroughput satellite to the target ground station.
 37. The highthroughput satellite of claim 15, wherein the digital processor is todigitally channelizing uplink data from the LEO satellite received overthe inter-satellite link and route the digitally channelized uplink datato a different ground terminal specified by the LEO satellite.
 38. Thehigh throughput satellite of claim 37, wherein the routing is carriedout in response to detection of a degraded feeder link to a targetground station.